This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A fundamental cause of and contributor to disability in older people is the involuntary loss of muscle mass and strength (sarcopenia), which eventually reduces function , thus increasing risk of falls and vulnerability to injury. Our general hypothesis is that nutritional factors and inactivity play significant roles in the development of sarcopenia. Thus, age-specific prolonged interventions including nutritional manipulations and/or exercise may help to reduce, stabilize, or even reverse the loss of muscle mass and strength with age. Our goal is to establish if specific interventions that can acutely increase muscle protein synthesis can also effectively translate into increased muscle mass and/or performance in older sedentary people, thus preventing frailty and promoting physical independence. To this end we will use stable isotope methodologies to measure muscle protein metabolism and contrast enhanced ultrasound to measure muscle perfusion, in order to determine if the treatments'acute effects can predict their chronic impact on muscle mass and function. Furthermore, we will also determine if chronic treatment leads to metabolic and/or vascular adaptations that may explain the measured changes in muscle mass and function. If we confirm that this type of supplementation can effectively improve muscle mass and strength in sedentary older subjects, it will be possible to test efficient supplements not only in frail elderly, but also in cases where caloric restriction is necessary or desirable, and where physical frailty is a potential risk (e.g., older obese and/or diabetic subjects, sarcopenic obesity).